1. Field of the Invention
The present invention relates to a tracking method and a tracking apparatus.
2. Background Art
In recent years, the introduction of an autonomous mobile unit such as a robot into the general environment such as a shop or facility has been examined. When a robot is introduced into the general environment, it is a problem whether the safety of the robot is assured. Particularly, under the environment where the robot and a person are coexistent, it is required that the robot recognizes the person and takes a safe operation for the person. On the other hand, it is important to assure the basic performance of the robot such as a smooth movement operation. Accordingly, when the robot is introduced into the general environment, a tradeoff between the assured safety and the assured basic performance is a problem.
Conventionally, when the robot recognizes a person, the robot stops at the site and waits for the person to leave away, or avoids the person while keeping an enough interval from the person. However, at the small shop or small scale facility, it is difficult to secure the interval between the robot and the person sufficiently. Accordingly, the robot has to stop at the site and let the person go away in such a case. However, the robot taking such a motion strategy has a bad work efficiency and is unusable for practical applications.
One of the reasons why such motion strategy must be taken is that the robot has less movement information of other mobile units. Accordingly, to realize the introduction of the robot into the general environment, it is important to improve techniques, such as detection technique for a mobile unit, tracking technique for a mobile unit, feature analysis technique for a mobile unit, and interaction technique between robots.
As examples of a system for detecting a mobile unit within a space, there are proposed a system using a surveillance camera and a system using a transmitter such as an ID tag. Furthermore, processes using these systems have been researched. Examples of such processes include person detection, position estimation, traffic line detection for a moving person, and action estimation for a moving person. Also, as an example of a method for detecting a mobile unit, there is proposed a method using optical flow. This method is effective for detecting the motion of a rigid single body such as one automobile or one ball, but this method easily causes a false detection for an object of multi-link structure such as a person, because it is difficult to treat its internal motion and interaction with other persons. JP-A 2006-127157 (KOKAI) describes a method for extracting the features of a mobile unit by time averaging of flow vectors. However, with this method, there is possibility that the features to be extracted may disappear by time average.
It is also researched that a point extracted from a camera image is translated from a camera screen onto a movement plane to estimate the movement amount of an object on the movement plane. JP-A 2006-33188 (KOKAI) describes a method for tracking an object by estimating the movement amount of the object on the movement plane using a speed vector. However, with this method, there is strong possibility that a meaningless motion contained in the significant motion of the person may be also detected. Also, if the speed vector is simply averaged over time to prevent this as previously described, there is strong possibility that the significant motion may also disappear.
Main purposes of the methods described in JP-A 2006-127157 (KOKAI) and JP-A 2006-33188 (KOKAI) are to investigate guest trend and to take crime prevention. With the method described in JP-A 2006-127157 (KOKAI) or JP-A 2006-33188 (KOKAI), information such as the position coordinate, moving speed, and residence time of a detected mobile unit is acquired. However, these kinds of information are not enough to support the motion of the autonomous mobile unit that autonomously moves within the shop or facility. Also, if only a client refers to these kinds of information exclusively, there is possibility that the movement of the autonomous mobile unit becomes movement based on the absolute viewpoint of the client.